1. Technical Field
This disclosure generally relates to an image forming apparatus, and more particularly, to an image forming apparatus including a recording head to eject ink droplets onto sheets of recording media.
2. Discussion of the Background Art
As image forming apparatuses, such as printers, facsimile machines, plotters, or multifunction machines including at least two of these functions, liquid-ejecting image forming apparatuses such as inkjet recording devices that use a recording head for ejecting ink droplets are known.
There are two types of liquid-ejecting image forming apparatuses. Serial-type image forming apparatuses form images using a recording head that ejects ink droplets onto a recording medium while moving in a main scanning direction. By contrast, line-type image forming apparatuses form images using a recording head that remains stationary while ejecting ink droplets.
In either case, the liquid-ejecting image forming apparatuses form images by ejecting the ink droplets from the recording head onto a sheet of recording media while the sheet is being transported.
In such liquid-ejecting image forming apparatuses, a need has arisen to increase image formation throughput, that is, image formation speed. One way to achieve that aim is to reduce the replacement time required to replace ink cartridges.
Accordingly, a known liquid-ejecting image forming apparatus uses a large-capacity ink cartridge that is replaceably attached to the image forming apparatus. Ink is supplied from the large-capacity ink cartridge via a supply tube to a sub-tank, which is also called a head tank, provided in an upper portion of the main body.
Although such an arrangement has advantages, it also has several drawbacks. For example, because the recording head ejects ink from nozzles onto the sheet, over time the ink tends to thicken or even solidify as solvent evaporates from the ink through the nozzle. In addition, dust tends to adhere to the nozzle, and air can get into the nozzle, all of which can cause ejection failure, resulting in the production of substandard images.
Therefore, liquid-ejecting image forming apparatuses typically include a maintenance unit or cleaning unit that removes waste ink from the recording head to maintain good printing performance of the recording head. The waste ink removed from the recording head is stored in a waste-ink tank or waste-ink container which is replaceable in order to extend the operational life of the image forming apparatus.
When the main tank and the waste-ink tank are replaced, the liquid-ejecting image forming apparatus must be deactivated. However, in such known liquid-ejecting image forming apparatuses, because separate detectors are used to detect removal of the ink cartridge and that of the waste-ink tank, its configuration is relatively complicated, and accordingly its cost is relatively high.
In view of the foregoing, there is a need to detect replacement of the ink cartridge as well as that of the waste-ink tank using a simple configuration.